1.
Microscope
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A microscope is an instrument used to see objects that are too small for the naked eye. The science of investigating small objects using such an instrument is called microscopy, microscopic means invisible to the eye unless aided by a microscope. There are many types of microscopes, the most common is the optical microscope, which uses light to image the sample. Other major types of microscopes are the microscope, the ultramicroscope. The earliest microscopes were single lens magnifying glasses with limited magnification which date at least as far back as the wide use of lenses in eyeglasses in the 13th century. Compound microscopes, which combine an objective lens with an eyepiece to view a real image, the actual inventor of the compound microscope is unknown although many claims have been made over the years. These include what may be a claim by the son of Zacharias Janssen that his father invented the microscope and telescope as early as 1590. Historians note the compound microscope did not appear in the Netherlands until the 1620s, giovanni Faber coined the name microscope for the compound microscope Galileo submitted to the Accademia dei Lincei in 1625. The first detailed account of the construction of living tissue based on the use of a microscope did not appear until 1644, in Giambattista Odiernas Locchio della mosca. It was not until the 1660s and 1670s that the microscope was used extensively for research in Italy, marcello Malpighi in Italy began the analysis of biological structures, beginning with the lungs. Robert Hookes Micrographia had an impact, largely because of its impressive illustrations. A significant contribution came from Antonie van Leeuwenhoek who achieved up to 300 times magnification using a single lens microscope. He sandwiched a very small glass ball lens between the holes in two metal plates riveted together, and with a needle attached to mount the specimen. Then, Van Leeuwenhoek re-discovered red blood cells and spermatozoa, on 9 October 1676, he reported the discovery of micro-organisms. The performance of light microscopy depends as much on how the sample is illuminated as on how it is observed, early instruments were limited until this principle was fully appreciated and developed, and until electric lamps were available as light sources. In 1893 August Köhler developed a key principle of sample illumination, Köhler illumination and this method of sample illumination produces even lighting and overcomes the limited contrast and resolution imposed by early techniques of sample illumination. In the early 20th century a significant alternative to light microscopy was developed, ernst Ruska started development of the first electron microscope in 1931 which was the transmission electron microscope. The transmission electron microscope works on the principle as an optical microscope but uses electrons in the place of light
2.
Printer (computing)
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In computing, a printer is a peripheral which makes a persistent human-readable representation of graphics or text on paper or similar physical media. The worlds first computer printer was a 19th-century mechanically driven apparatus invented by Charles Babbage for his difference engine, the plotter was used for those requiring high quality line art like blueprints. Laser printers using PostScript mixed text and graphics, like dot-matrix printers, by 1990, most simple printing tasks like fliers and brochures were now created on personal computers and then laser printed, expensive offset printing systems were being dumped as scrap. The HP Deskjet of 1988 offered the same advantages as laser printer in terms of flexibility, inkjet systems rapidly displaced dot matrix and daisy wheel printers from the market. By the 2000s high-quality printers of this sort had fallen under the price point. Even the desire for printed output for offline reading while on mass transit or aircraft has been displaced by e-book readers, today, traditional printers are being used more for special purposes, like printing photographs or artwork, and are no longer a must-have peripheral. Starting around 2010, 3D printing became an area of intense interest and these devices are in their earliest stages of development and have not yet become commonplace. Personal printers are designed to support individual users, and may be connected to only a single computer. These printers are designed for low-volume, short-turnaround print jobs, requiring minimal setup time to produce a copy of a given document. However, they are generally slow devices ranging from 6 to around 25 pages per minute, however, this is offset by the on-demand convenience. Some printers can print documents stored on cards or from digital cameras. Networked or shared printers are designed for high-volume, high-speed printing and they are usually shared by many users on a network and can print at speeds of 45 to around 100 ppm. The Xerox 9700 could achieve 120 ppm, a virtual printer is a piece of computer software whose user interface and API resembles that of a printer driver, but which is not connected with a physical computer printer. It is called a printer by analogy with a printer which produces a two-dimensional document by a similar process of depositing a layer of ink on paper. The choice of print technology has an effect on the cost of the printer and cost of operation, speed, quality and permanence of documents. Some printer technologies dont work with certain types of physical media, cheques can be printed with liquid ink or on special cheque paper with toner anchorage so that alterations may be detected. The machine-readable lower portion of a cheque must be printed using MICR toner or ink, banks and other clearing houses employ automation equipment that relies on the magnetic flux from these specially printed characters to function properly. The following printing technologies are found in modern printers, A laser printer rapidly produces high quality text
3.
Inkjet printing
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Inkjet printing is a type of computer printing that recreates a digital image by propelling droplets of ink onto paper, plastic, or other substrates. Inkjet printers are the most commonly used type of printer, the concept of inkjet printing originated in the 20th century, and the technology was first extensively developed in the early 1950s. Starting in the late 1970s inkjet printers that could reproduce digital images generated by computers were developed, mainly by Epson, Hewlett-Packard, in the worldwide consumer market, four manufacturers account for the majority of inkjet printer sales, Canon, HP, Epson, and Brother. The emerging ink jet material deposition market also uses inkjet technologies, typically printheads using piezoelectric crystals, the technology has been extended and the ″ink″ can now also comprise living cells, for creating biosensors and for tissue engineering. There are two main technologies in use in contemporary inkjet printers, continuous and Drop-on-demand, the continuous inkjet method is used commercially for marking and coding of products and packages. In 1867 Lord Kelvin patented the syphon recorder, which recorded telegraph signals as a trace on paper using an ink jet nozzle deflected by a magnetic coil. The first commercial devices were introduced in 1951 by Siemens, the ink droplets are subjected to an electrostatic field created by a charging electrode as they form, the field varies according to the degree of drop deflection desired. This results in a controlled, variable electrostatic charge on each droplet, charged droplets are separated by one or more uncharged guard droplets to minimize electrostatic repulsion between neighbouring droplets. The more highly charged droplets are deflected to a greater degree, only a small fraction of the droplets is used to print, the majority being recycled. CIJ is one of the oldest ink jet technologies in use and is fairly mature, viscosity is monitored and a solvent is added to counteract solvent loss. Drop-on-demand is divided into thermal DOD and piezoelectric DOD, most consumer inkjet printers, including those from Canon, Hewlett-Packard, and Lexmark, use the thermal inkjet process. Vaughts work started in late 1978 with a project to develop fast, low-cost printing, the team at HP found that thin-film resistors could produce enough heat to fire an ink droplet. Two years later the HP and Canon teams found out about each others work, in the thermal inkjet process, the print cartridges consist of a series of tiny chambers, each containing a heater, all of which are constructed by photolithography. The inks involved are usually water-based and use either pigments or dyes as the colorant, the inks must have a volatile component to form the vapor bubble, otherwise droplet ejection cannot occur. As no special materials are required, the print head is generally cheaper to produce than in other inkjet technologies, most commercial and industrial inkjet printers and some consumer printers use a piezoelectric material in an ink-filled chamber behind each nozzle instead of a heating element. When a voltage is applied, the material changes shape, generating a pressure pulse in the fluid. A DOD process uses software that directs the heads to apply between zero and eight droplets of ink per dot, only where needed, piezo inkjet technology is often used on production lines to mark products. For instance, the date is often applied to products with this technique, in this application the head is stationary
4.
Laser printing
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Laser printing is an electrostatic digital printing process. It produces high-quality text and graphics by repeatedly passing a laser beam back, the drum then selectively collects electrically charged powdered ink, and transfers the image to paper, which is then heated in order to permanently fuse the text and/or imagery. As with digital photocopiers, laser printers employ a xerographic printing process, however, laser printing differs from analog photocopiers in that the image is produced by the direct scanning of the medium across the printers photoreceptor. This enables laser printing to copy images more quickly than most photocopiers, invented at Xerox PARC in the 1970s, laser printers were introduced for the office and then home markets in subsequent years by IBM, Canon, Xerox, Apple, Hewlett-Packard and many others. Over the decades, quality and speed have increased as price has fallen, in the 1960s, the Xerox Corporation held a dominant position in the photocopier market. In 1969, Gary Starkweather, who worked in Xeroxs product development department, had the idea of using a beam to draw an image of what was to be copied directly onto the copier drum. After transferring to the recently formed Palo Alto Research Center in 1971, in 1972, Starkweather worked with Butler Lampson and Ronald Rider to add a control system and character generator, resulting in a printer called EARS —which later became the Xerox 9700 laser printer. The first commercial implementation of a printer was the IBM3800 in 1976. It was designed for data centers, where it replaced line printers attached to mainframe computers, the IBM3800 was used for high-volume printing on continuous stationery, and achieved speeds of 215 pages per minute, at a resolution of 240 dots per inch. Over 8,000 of these printers were sold, the Xerox 9700 was brought to market in 1977. Unlike the IBM3800, the Xerox 9700 was not targeted to any particular existing printers. The Xerox 9700 excelled at printing high-value documents on paper with varying content. In 1979, inspired by the Xerox 9700s commercial success, Japanese camera and optics company, Canon, developed a low-cost, desktop laser printer, Canon then began work on a much-improved print engine, the Canon CX, resulting in the LBP-CX printer. Lacking experience in selling to computer users, Canon sought partnerships with three Silicon Valley companies, Diablo Data Systems, Hewlett-Packard, and Apple Computer, the first laser printer designed for office use reached market in 1981, the Xerox Star 8010. The system used a metaphor that was unsurpassed in commercial sales. Although it was innovative, the Star workstation was an expensive system, affordable only to a fraction of the businesses. The first laser printer intended for mass-market sales was the HP LaserJet, released in 1984, it used the Canon CX engine, the LaserJet was quickly followed by printers from Brother Industries, IBM, and others. First-generation machines had large photosensitive drums, of greater than the loaded papers length
5.
Typewriter
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A typewriter is a mechanical or electromechanical machine for writing characters similar to those produced by printers movable type. A typewriter operates by means of keys that strike a ribbon to transmit ink or carbon impressions onto paper, typically, a single character is printed on each key press. The machine prints characters by making ink impressions of type elements similar to the used in movable type letterpress printing. At the end of the century, the term typewriter was also applied to a person who used a typing machine. After its invention in the 1860s, the quickly became an indispensable tool for practically all writing other than personal handwritten correspondence. It was widely used by writers, in offices. As with the automobile, telephone, and telegraph, a number of people contributed insights, historians have estimated that some form of typewriter was invented 52 times as thinkers tried to come up with a workable design. Some of the early typing instruments, In 1575 an Italian printmaker, Francesco Rampazzetto, invented the scrittura tattile, in 1714, Henry Mill obtained a patent in Britain for a machine that, from the patent, appears to have been similar to a typewriter. In 1802 Italian Agostino Fantoni developed a particular typewriter to enable his blind sister to write, in 1808 Italian Pellegrino Turri invented a typewriter. He also invented carbon paper to provide the ink for his machine, in 1823 Italian Pietro Conti di Cilavegna invented a new model of typewriter, the tachigrafo, also known as tachitipo. In 1829, William Austin Burt patented a machine called the Typographer which, the Science Museum describes it merely as the first writing mechanism whose invention was documented, but even that claim may be excessive, since Turris invention pre-dates it. Even in the hands of its inventor, this machine was slower than handwriting, Burt and his promoter John D. Sheldon never found a buyer for the patent, so the invention was never commercially produced, because the typographer used a dial, rather than keys, to select each character, it was called an index typewriter rather than a keyboard typewriter. Index typewriters of that era resemble the squeeze-style embosser from the 1960s more than they resemble the modern keyboard typewriter, by the mid-19th century, the increasing pace of business communication had created a need for mechanization of the writing process. Stenographers and telegraphers could take down information at rates up to 130 words per minute, from 1829 to 1870, many printing or typing machines were patented by inventors in Europe and America, but none went into commercial production. Charles Thurber developed multiple patents, of which his first in 1843 was developed as an aid to the blind, in 1855, the Italian Giuseppe Ravizza created a prototype typewriter called Cembalo scrivano o macchina da scrivere a tasti. It was a machine that let the user see the writing as it was typed. In 1861, Father Francisco João de Azevedo, a Brazilian priest, made his own typewriter with basic materials and tools, such as wood, in that same year the Brazilian emperor D
6.
Daisy wheel printing
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Daisy wheel printing is an impact printing technology invented in 1969 by David S. Lee at Diablo Data Systems. Daisy wheel printing was used in typewriters, word processors and computers from 1972. The daisy wheel is considered to be so named because of its resemblance to the daisy flower, by 1980 daisy wheel printers had become the dominant technology for high-quality print. Dot-matrix impact, thermal, or line printers were used where speed was required. Daisy wheel technology is now only in some electronic typewriters. In 1889 Arthur Irving Jacobs patented a daisy wheel design that was used on the Victor index typewriter, a. H. Reiber of Teletype Corporation received U. S. Patent 2,146,380 in 1939 for a daisy wheel printer, in 1972 a team at Diablo Systems led by engineer David S.4 cps. Xerox acquired Diablo that same year, following which Lee departed to set up Qume Corporation in 1973, xeroxs Office Product Division had already been buying Diablo printers for its Redactron text editors. After 7 years trying to make Diablo profitable, the OPD focused on developing and selling the Diablo 630 which was bought by companies such as Digital Equipment Corporation. The Diablo 630 could produce letter quality output as good as that produced by an IBM Selectric or Selectric-based printer, a further advantage was that it supported the entire ASCII printing character set. Its servo-controlled carriage also permitted the use of proportional spaced fonts, Xerox later adapted Diablos daisy wheel technology into a typewriter that sold for less than $50. An automated factory was built near Dallas that took less than 30 minutes to assemble a Xerox typewriter, the Xerox typewriter was well received but never achieved the projected sales numbers due to the advent of the PC and word processing software. The typewriter was modified to be compatible with PCs but the engineering which made it a low cost device reduced its flexibility. The heart of the system is a metal or plastic daisy wheel holding an entire character set as raised characters moulded on each petal. In use a servo motor rotates the wheel to position the required character between the hammer and the ribbon. The solenoid-operated hammer then fires, driving the character type onto the ribbon, the daisy wheel and hammer are mounted on a sliding carriage similar to that used by dot matrix printers. Different typefaces and sizes can be used by replacing the daisy wheel, however, printing a document with frequent font changes and thus requiring frequent wheel changes was a tedious task. Like all other impact printers, daisy wheel printers are noisy, most daisy-wheel printers could print a line and then, using built-in memory, print the following line backwards, from right to left
7.
Line printer
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The line printer is an impact printer that prints one entire line of text at a time. It is mostly associated with unit record equipment and the days of digital computing. Print speeds of 600 lines-per-minute were achieved in the 1950s, later increasing to as much as 1200 lpm, Line printers print a complete line at a time and have speeds in the range of 150 to 2500 lines per minute. The different types of printers are drum printers and chain printers. Other non-impact technologies have also used, as thermal line printers were popular in the 1970s and 1980s. Many impact printers, such as the printer and dot matrix printer. Line printers were much faster, as each impact printed an entire line, in a typical drum printer design, a fixed font character set is engraved onto the periphery of a number of print wheels, the number matching the number of columns the printer could print. The wheels, joined to form a large drum, spin at high speed and paper, because the drum carrying the letterforms remains in constant motion, the strike-and-retreat action of the hammers had to be very fast. Typically, they were driven by voice coils mounted on the part of the hammer. Often the character sequences are staggered around the drum, shifting with each column and this obviates the situation whereby all of the hammers fire simultaneously when printing a line that consists of the same character in all columns, such as a complete line of dashes. Lower-cost printers did not use a hammer for each column, instead, a hammer was provided for every other column and the entire hammer bank was arranged to shift left and right, driven by another one voice coil. But in this way, only half the number of hammers, magnets, at least one low-cost printer, made by CDC, achieved the same end by moving the paper laterally while keeping the hammer bank at rest. Dataproducts was a vendor of drum printers, often selling similar models with both a full set of hammers and a half set of hammers. Chain printers placed the type on moving bars, as with the drum printer, as the correct character passed by each column, a hammer was fired from behind the paper. Compared to drum printers, chain printers had the advantage that the chain could usually be changed by the operator. By selecting chains that had a character set, the printer could print much faster than if the chain contained the entire upper- and lower-case alphabet, numbers. This was because, with many instances of the numbers appearing in the chain. Common letters and symbols would appear often on the chain
8.
Dot matrix printing
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However, unlike a typewriter or daisy wheel printer, letters are drawn out of a dot matrix, and thus, varied fonts and arbitrary graphics can be produced. Each dot is produced by a metal rod, also called a wire or pin. Facing the ribbon and the paper is a guide plate named ribbon mask holder or protector. It is pierced with holes to serve as guides for the pins and this plate may be made of hard plastic or an artificial jewel such as sapphire or ruby. The portion of the containing the pins is called the print head. When running the printer, it generally prints one line of text at a time, there are two approaches to achieve this, The common serial dot matrix printers use a horizontally moving print head. The print head can be thought of featuring a vertical column of seven or more pins approximately the height of a character box. Thereby, up to 48 pins can be used to form the characters of a line while the print head moves horizontally. In a considerably different configuration, so called line dot matrix printers use a print head almost as wide as the paper path utilizing a horizontal line of thousands of pins for printing. Sometimes two horizontally slightly displaced rows are used to improve the effective dot density through interleaving, while still line-oriented, these printers for the professional heavy-duty market effectively print a whole line at once while the paper moves forward below the print head. The printing speed of serial dot matrix printers with moving heads varies from 30 to 1550 cps, in contrast to this, line matrix printers are capable of printing much more than 1000 cps, resulting in a throughput of up to 800 pages/hour. Because the printing involves mechanical pressure, both of these types of printers can create carbon copies and carbonless copies and these machines can be highly durable. A variation on the dot matrix printer was the cross hammer dot printer, the smooth cylindrical roller of a conventional printer was replaced by a spinning, fluted cylinder. The print head was a hammer, with a vertical projecting edge. Where the vertical edge of the hammer intersected the horizontal flute of the cylinder, compressing the paper, characters were built up of multiple dots. Although nearly all inkjet, thermal, and laser printers also print closely spaced dots rather than lines or characters. In 1925, Rudolf Hell invented the Hellschreiber, an early facsimile-like dot matrix-based teletypewriter device, like the earlier Hellschreiber, it still used electromechanical means of coding and decoding, but it used a start-stop method rather than synchronous transmission for communication. In 1956, while he was employed at Telefonbau und Normalzeit GmbH, the device was introduced to the Deutsche Bundespost, when Preikschat emigrated into the USA in 1957 he sold the rights to utilize the applications in any countries to TuN
9.
History of printing
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The history of printing goes back to the duplication of images by means of stamps in very early times. In both China and Egypt, the use of stamps for seals preceded the use of larger blocks. In China, India and Europe, the printing of cloth certainly preceded the printing of paper or papyrus, the process is essentially the same - in Europe special presentation impressions of prints were often printed on silk until the seventeenth century. Block printing is a technique for printing text, images or patterns used widely throughout East Asia both as a method of printing on textiles and later, under the influence of Buddhism, on paper. As a method of printing on cloth, the earliest surviving examples from China date to about 220, ukiyo-e is the best known type of Japanese woodblock art print. Most European uses of the technique on paper are covered by the term woodcut, the worlds earliest printer printed fragments to survive are from China and are of silk printed with flowers in three colours from the Han Dynasty. It reached Europe, via the Islamic world, and by around 1400 was being used on paper for old master prints, the third oldest wood-block printed book ever found after Mugujeonggwang great Dharani sutraand Hyakumantō Darani is the Diamond Sutra. It carries a date of the 13th day of the moon of the ninth year of the Xiantong era. A number of printed dhāraṇīs, however, predate the Diamond Sūtra by about two hundred years, in Buddhism, great merit is thought to accrue from copying and preserving texts. The fourth-century master listed the copying of scripture as the first of ten essential religious practices and this ‘cult of the book’ led to techniques for reproducing texts in great numbers, especially the short prayers or charms known as dhāraṇīs. Stamps were carved for printing these prayers on clay tablets from at least the seventh century, especially popular was the Pratītyasamutpāda Gāthā, a short verse text summing up Nāgārjunas philosophy of causal genesis or dependent origination. Nagarjuna lived in the centuries of the current era and the Buddhist Creed. This tradition was transmitted to China and Tibet with Buddhism, Printing text from woodblocks does not, however, seem to have been developed in India. Printing with a press was practiced in Christian Europe as a method for printing on cloth and these prints were produced in very large numbers from about 1425 onwards. Around the mid-century, block-books, woodcut books with text and images, usually carved in the same block, emerged as a cheaper alternative to manuscripts. These were all heavily illustrated works, the bestsellers of the day, repeated in many different block-book versions, the Ars moriendi. In Europe, from about 1450 they were commonly used to colour old master prints printed in black and white. This was especially the case with playing-cards, which continued to be coloured by stencil long after most other subjects for prints were left in black, stenciling back in the 27th century BCE was different
10.
Woodblock printing
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Woodblock printing is a technique for printing text, images or patterns used widely throughout East Asia and originating in China in antiquity as a method of printing on textiles and later paper. Ukiyo-e is the best known type of Japanese woodblock art print, most European uses of the technique for printing images on paper are covered by the art term woodcut, except for the block-books produced mainly in the 15th century. Prior to the invention of printing, seals and stamps were used for making impressions. The oldest of these came from Mesopotamia and Egypt. A few much larger brick stamps for marking clay bricks survive from Akkad from around 2270 BC. There are also Roman lead pipe inscriptions of some length that were stamped, however none of these used ink, which is necessary for printing, but stamped marks into relatively soft materials. In both China and Egypt, the use of stamps for seals preceded the use of larger blocks. In Europe and India, the printing of cloth certainly preceded the printing of paper or papyrus, the process is essentially the same—in Europe special presentation impressions of prints were often printed on silk until at least the 17th century. The block was cut along the grain of the wood and it is necessary only to ink the block and bring it into firm and even contact with the paper or cloth to achieve an acceptable print. The content would of course print in reverse or mirror-image, a further complication when text was involved, the art of carving the woodcut is technically known as xylography, though the term is rarely used in English. For colour printing, multiple blocks are used, each for one colour, multiple colours can be printed by keying the paper to a frame around the woodblocks. There are three methods of printing to consider, Stamping Used for many fabrics, and most early European woodcuts. These items were printed by putting paper or fabric on a table or a surface with the block on top, and pressing, or hammering. Rubbing Apparently the most common for Far Eastern printing, Used for European woodcuts and block-books later in the 15th century, and very widely for cloth. The block is placed face side up on a table, with the paper or fabric on top, the back of the paper or fabric is rubbed with a hard pad, a flat piece of wood, a burnisher, or a leather frotton. Printing in a press Presses only seem to have used in Asia in relatively recent times. Simple weighted presses may have used in Europe, but firm evidence is lacking. A deceased Abbess of Mechelen in Flanders in 1465 had unum instrumentum ad imprintendum scripturas et ymagines, cum 14 aliis lapideis printis which is probably too early to be a Gutenberg-type printing press in that location
11.
Printing press
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A printing press is a device for applying pressure to an inked surface resting upon a print medium, thereby transferring the ink. The printing press was invented in the Holy Roman Empire by the German Johannes Gutenberg around 1440, the printing press spread within several decades to over two hundred cities in a dozen European countries. By 1500, printing presses in operation throughout Western Europe had already produced more than twenty million volumes, in the 16th century, with presses spreading further afield, their output rose tenfold to an estimated 150 to 200 million copies. The operation of a press became so synonymous with the enterprise of printing that it lent its name to a new branch of media. The sharp rise of learning and literacy amongst the middle class led to an increased demand for books which the time-consuming hand-copying method fell far short of accommodating. Technologies preceding the press led to the presss invention included, manufacturing of paper, development of ink, woodblock printing. At the same time, a number of products and technological processes had reached a level of maturity which allowed their potential use for printing purposes. The device was used from very early on in urban contexts as a cloth press for printing patterns. Gutenberg may have also inspired by the paper presses which had spread through the German lands since the late 14th century. Gutenberg adopted the design, thereby mechanizing the printing process. Printing, however, put a demand on the quite different from pressing. Gutenberg adapted the construction so that the power exerted by the platen on the paper was now applied both evenly and with the required sudden elasticity. To speed up the process, he introduced a movable undertable with a plane surface on which the sheets could be swiftly changed. The known examples range from Germany to England to Italy, however, the various techniques employed did not have the refinement and efficiency needed to become widely accepted. Gutenberg greatly improved the process by treating typesetting and printing as two separate work steps, a goldsmith by profession, he created his type pieces from a lead-based alloy which suited printing purposes so well that it is still used today. The mass production of metal letters was achieved by his key invention of a hand mould. Another factor conducive to printing arose from the existing in the format of the codex. Considered the most important advance in the history of the prior to printing itself
12.
Etching
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Etching is traditionally the process of using strong acid or mordant to cut into the unprotected parts of a metal surface to create a design in intaglio in the metal. In modern manufacturing, other chemicals may be used on other types of material, as a method of printmaking, it is, along with engraving, the most important technique for old master prints, and remains in wide use today. In a number of variants such as microfabrication etching and photochemical milling it is a crucial technique in much modern technology. In traditional pure etching, a plate is covered with a waxy ground which is resistant to acid. The artist then scratches off the ground with an etching needle where he or she wants a line to appear in the finished piece. The échoppe, a tool with an oval section, is also used for swelling lines. The plate is dipped in a bath of acid, technically called the mordant or etchant. The acid bites into the metal where it is exposed, leaving behind lines sunk into the plate, the remaining ground is then cleaned off the plate. The plate is inked all over, and then the ink wiped off the surface, the plate is then put through a high-pressure printing press together with a sheet of paper. The paper picks up the ink from the lines, making a print. The process can be repeated many times, typically several hundred impressions could be printed before the shows much sign of wear. The work on the plate can also be added to by repeating the whole process, Etching has often been combined with other intaglio techniques such as engraving or aquatint. The process as applied to printmaking is believed to have been invented by Daniel Hopfer of Augsburg, Hopfer was a craftsman who decorated armour in this way, and applied the method to printmaking, using iron plates. Apart from his prints, there are two examples of his work on armour, a shield from 1536 now in the Real Armeria of Madrid. The switch to copper plates was made in Italy. On the other hand, the handling of the ground and acid need skill and experience, prior to 1100 AD, the New World Hohokam independently utilized the technique of acid etching in marine shell designs. Jacques Callot from Nancy in Lorraine made important technical advances in etching technique and he developed the échoppe, a type of etching-needle with a slanting oval section at the end, which enabled etchers to create a swelling line, as engravers were able to do. Callot also appears to have responsible for an improved, harder, recipe for the etching ground
